THE SPACE INFORMATION AND CONTROL SYSTEM AVAILABILITY ASSESSMENT CONSIDERING ELIMINATION OF SOFTWARE FAULTS AFTER ON-LINE VERIFICATION

Вячеслав Сергійович Харченко, Юрій Леонідович Поночовний, Артем Володимирович Боярчук, Ілона Олександрівна Черницька, Володимир Станіславович Воронянський

Abstract


The paper deals the multi-fragmental model of the two-channel space on-board information and control system of piloted spaceship. The model describes process of on-line software verification considering subsequent elimination of detected software faults. To take into account the change of software failure rate, the apparatus of regular multi-fragmental Markov’s models is used. The algorithm of determining sets of state fragments, states, transitions is proposed. It is considered the most widespread architecture of the information-control system, which includes two redundant hardware channels. Each channel has the same software version. After a failure caused by software faults, the information and control system is restored by restarting. Particularity of the researched system is performing of on-line software verification during its operation. The state of verification is considered as down-state on availability assessing. After onset software faults, degradation of program functions does not occur. The system is recoveredafter the failed state and continues functioning. For the estimation of the availability function, the Markov’s model for different sets of input data is researched. For that Matlab programs were developed. To solve the system of differential equations, an embedded Matlab ode15s solver is used. It is revealed that with increasing probability of faults detection during on-linesoftware verification, the availability of the system will increase at the end of the time interval of the model study. In order to accelerate the transition of the availability to stationary state, it is necessary to carry out more frequent verification procedures and try to eliminate a greater number of software faults in one check. In the initial period of operation, the availability of systems with planned on-line verification is lower than that of systems without fixing software faults. According to the results of the simulation, conclusions about the influence of the time parameters of the verification on the fault elimination intensity and the minimum of availability functions are formulated.


Keywords


space system; multifragmental Markov’s model; on-line verification; software faults

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